Tissue Organisation

Question 1

What hold cells together?

Answer 1

Cell-cell adhesion
Internal-external scaffolding
Extracellular matrix proteins like collagen and laminin
Close proximity (pressure effect)

Question 2

How do epithelial and connective tissue differ in organisation?

Answer 2

In connective tissue that cells are far apart, ECM is plentiful in connective tissue and the matrix which bears most of the mechanical stress is rich in fibrous polymers such as collagen. Cell-cell adhesion is very rare.

In epithelial cells cells are close together and cell-cell adhesion is very common. ECM is not very common and generally only consist of the basal lamina that lies at the basal part of the epithelial cells. So there are adhesions between cells but also to the underlying basal lamina.

Question 3

What is the primary cell of the connective tissue?

Answer 3

Mesenchymal stem cells which is a type of immature fibroblasts. In case of connective tissue it is fibroblasts?

Question 4

What can mesenchymal stem cells turn into?

Answer 4

Fibroblasts, adipocytes, muscle cells, stromal cells, chondrocytes, osteocytes.

Question 5

What do fibroblasts produce?

Answer 5

Collagen, fibronectin and laminin

Question 6

What is the third important component of connective tissue?

Answer 6

Ground substance such as glucosaminoglycans e.g. hyaluronic acid

Question 7

What are the three main components of connective tissue?

Answer 7

Cells such as fibroblasts, adipocytes and reticular cells
Fibres such as collagen, elastin, reticular fibres, fibronectin, fibrillin, laminin
Ground substance such as hyaluronic acid

Question 8

What are the functions of connective tissue?

Answer 8

binding and supporting
protecting
insulating
energy reserve
transporting substances (blood)
separation of tissues

Question 9

Define epithelial cells.

Answer 9

They line all cavities and free surfaces of the body.

Closely packed and they have a basement membrane.

Question 10

Why is the adherence system in epithelial cells important?

Answer 10

Because it helps epithelial cells stick together. It also allows communication between cells and inhibit the movement of water, solutes, and cells from one body compartment to another.

Question 11

What are the five lateral adherence systems found on epithelial cells?

Answer 11

Tight junctions (at the very top, prevents movement of large molecules)
Adherens junctions (found below TJ, actin filaments link to E-cadherin proteins)
Desmosomes (in the middle, cytokeratin links to E-cadherin)
Gap junctions (allows free movement of small molecules)
Cell adhesion molecules (Integrins, Selectin, and CAM)

Question 12

What are three basal adherence systems found on epithelial cells?

Answer 12

Hemi-desmosomes
Focal-adhesion
Integrins

Question 13

What is an essential ion that is needed for these adherence systems to work?

Answer 13

Ca2+

Question 14

What is the mucosal membrane?

Answer 14

A structure that lines all the moist hollow internal organs of the body.
It is continuous to the skin at various body openings.

Question 15

What do most mucous membranes secrete? What does the secretion consist of?

Answer 15

Mucus, a thick protective fluid.

Consists of proteins, electrolytes, enzymes, immunoglobulins.

Question 16

What are the functions of the mucous membrane?

Answer 16

Stop pathogens and dirt from entering the body
Prevent dehydration
Lubricate the surface

Question 17

What are some examples of where mucosal membrane can be found?

Answer 17

GI - tract
Urinary tract
Resp. tract

Question 18

What are the layers GI - tract?

Answer 18

Mucosa (ep. cells + basal lamina + lamina propria (conn. tissue))
Muscularis mucosal
Submucosa
Muscularis externae
Serosa

Question 19

What are the functions of the mucosal membrane in the GI - tract?

Answer 19

Prevent ingression of pathogens
Absorb substances from lumen
Move contents and expel waste

Question 20

In the Urinary Tract where can you find muscle layers?

Answer 20

In the ureter and bladder. In any other part it is not needed due to gravity.

Question 21

What are the layers of the trachea and primary bronchi?

Answer 21

Mucosa
Submucosa
Hyaline cartilage

Question 22

Why are secretions from the epithelium and submucosal glands of the trachea and bronchi important?

Answer 22

They contain a sticky mucus which dirt will stick to.
Serum proteins that lubricate the surface
Lyzozyme that destroy bacteria
Anti-proteases that inactivate bacterial enzymes
Cilia from pseudo stratified epithelium that makes up the mucociliary escalator

Question 23

What are the layers of the secondary and tertiary bronchi?

Answer 23

Mucosa
Muscularis mucosae
Submucosa
Hyaline cartilage

Question 24

What is a definition of mucous membrane?

Answer 24

Epithelial cells, basal lamina and lamina propria.